\begin{tikzpicture}
	\pgfmathsetmacro{\r}{2}
	\tkzDefPoints{-\r/0/A, 0/0/O, \r/0/D}
	\tkzDefPoint(45:\r){C}
	\tkzDefPoint(120:\r){B}

	\tkzDrawSegments(O,A  O,B  O,C  O,D)
	\tkzLabelPoints[below](A, O, D)
	\tkzLabelPoints[right](B, C)
\end{tikzpicture}

